Add extms support to master key generation.

Update master secret calculation to support extended master secret.
TLS 1.2 client authentication adds a complication because we need to
cache the handshake messages. This is simpllified however because
the point at which the handshake hashes are calculated for extended
master secret is identical to that required for TLS 1.2 client
authentication (immediately after client key exchange which is also
immediately before certificate verify).
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

ssl/d1_srvr.c

@@ -655,17 +655,19 @@ int dtls1_accept(SSL *s)
                 s->init_num = 0;
                 if (!s->session->peer)
                     break;
-                /*
-                 * For sigalgs freeze the handshake buffer at this point and
-                 * digest cached records.
-                 */
                 if (!s->s3->handshake_buffer) {
                     SSLerr(SSL_F_DTLS1_ACCEPT, ERR_R_INTERNAL_ERROR);
                     return -1;
                 }
-                s->s3->flags |= TLS1_FLAGS_KEEP_HANDSHAKE;
-                if (!ssl3_digest_cached_records(s))
-                    return -1;
+                /*
+                 * For sigalgs freeze the handshake buffer. If we support
+                 * extms we've done this already.
+                 */
+                if (!(s->s3->flags & SSL_SESS_FLAG_EXTMS)) {
+                    s->s3->flags |= TLS1_FLAGS_KEEP_HANDSHAKE;
+                    if (!ssl3_digest_cached_records(s))
+                        return -1;
+                }
             } else {
                 s->state = SSL3_ST_SR_CERT_VRFY_A;
                 s->init_num = 0;

ssl/s3_clnt.c

@@ -3150,7 +3150,15 @@ int ssl3_send_client_verify(SSL *s)
             }
             s2n(u, p);
             n = u + 4;
-            if (!ssl3_digest_cached_records(s))
+            /*
+             * For extended master secret we've already digested cached
+             * records.
+             */
+            if (s->session->flags & SSL_SESS_FLAG_EXTMS) {
+                BIO_free(s->s3->handshake_buffer);
+                s->s3->handshake_buffer = NULL;
+                s->s3->flags &= ~TLS1_FLAGS_KEEP_HANDSHAKE;
+            } else if (!ssl3_digest_cached_records(s))
                 goto err;
         } else
 #ifndef OPENSSL_NO_RSA

ssl/s3_srvr.c

@@ -620,17 +620,19 @@ int ssl3_accept(SSL *s)
                 s->init_num = 0;
                 if (!s->session->peer)
                     break;
-                /*
-                 * For sigalgs freeze the handshake buffer at this point and
-                 * digest cached records.
-                 */
                 if (!s->s3->handshake_buffer) {
                     SSLerr(SSL_F_SSL3_ACCEPT, ERR_R_INTERNAL_ERROR);
                     return -1;
                 }
-                s->s3->flags |= TLS1_FLAGS_KEEP_HANDSHAKE;
-                if (!ssl3_digest_cached_records(s))
-                    return -1;
+                /*
+                 * For sigalgs freeze the handshake buffer. If we support
+                 * extms we've done this already.
+                 */
+                if (!(s->s3->flags & SSL_SESS_FLAG_EXTMS)) {
+                    s->s3->flags |= TLS1_FLAGS_KEEP_HANDSHAKE;
+                    if (!ssl3_digest_cached_records(s))
+                        return -1;
+                }
             } else {
                 int offset = 0;
                 int dgst_num;

ssl/t1_enc.c

@@ -1070,13 +1070,41 @@ int tls1_generate_master_secret(SSL *s, unsigned char *out, unsigned char *p,
             len);
 #endif                          /* KSSL_DEBUG */
 
-
-    tls1_PRF(ssl_get_algorithm2(s),
-             TLS_MD_MASTER_SECRET_CONST, TLS_MD_MASTER_SECRET_CONST_SIZE,
-             s->s3->client_random, SSL3_RANDOM_SIZE,
-             co, col,
-             s->s3->server_random, SSL3_RANDOM_SIZE,
-             so, sol, p, len, s->session->master_key, buff, sizeof buff);
+    if (s->session->flags & SSL_SESS_FLAG_EXTMS) {
+        unsigned char hash[EVP_MAX_MD_SIZE * 2];
+        int hashlen;
+        /* If we don't have any digests cache records */
+        if (s->s3->handshake_buffer) {
+            /*
+             * keep record buffer: this wont affect client auth because we're
+             * freezing the buffer at the same point (after client key
+             * exchange and before certificate verify)
+             */
+            s->s3->flags |= TLS1_FLAGS_KEEP_HANDSHAKE;
+            ssl3_digest_cached_records(s);
+        }
+        hashlen = ssl_handshake_hash(s, hash, sizeof(hash));
+#ifdef SSL_DEBUG
+        fprintf(stderr, "Handshake hashes:\n");
+        BIO_dump_fp(stderr, (char *)hash, hashlen);
+#endif
+        tls1_PRF(ssl_get_algorithm2(s),
+                 TLS_MD_EXTENDED_MASTER_SECRET_CONST,
+                 TLS_MD_EXTENDED_MASTER_SECRET_CONST_SIZE,
+                 hash, hashlen,
+                 co, col,
+                 NULL, 0,
+                 so, sol, p, len, s->session->master_key, buff, sizeof buff);
+        OPENSSL_cleanse(hash, hashlen);
+    } else {
+        tls1_PRF(ssl_get_algorithm2(s),
+                 TLS_MD_MASTER_SECRET_CONST,
+                 TLS_MD_MASTER_SECRET_CONST_SIZE,
+                 s->s3->client_random, SSL3_RANDOM_SIZE,
+                 co, col,
+                 s->s3->server_random, SSL3_RANDOM_SIZE,
+                 so, sol, p, len, s->session->master_key, buff, sizeof buff);
+    }
 #ifdef SSL_DEBUG
     fprintf(stderr, "Premaster Secret:\n");
     BIO_dump_fp(stderr, (char *)p, len);
@@ -1175,6 +1203,9 @@ int tls1_export_keying_material(SSL *s, unsigned char *out, size_t olen,
     if (memcmp(val, TLS_MD_MASTER_SECRET_CONST,
                TLS_MD_MASTER_SECRET_CONST_SIZE) == 0)
         goto err1;
+    if (memcmp(val, TLS_MD_EXTENDED_MASTER_SECRET_CONST,
+               TLS_MD_EXTENDED_MASTER_SECRET_CONST_SIZE) == 0)
+        goto err1;
     if (memcmp(val, TLS_MD_KEY_EXPANSION_CONST,
                TLS_MD_KEY_EXPANSION_CONST_SIZE) == 0)
         goto err1;

ssl/tls1.h

@@ -782,7 +782,7 @@ SSL_CTX_callback_ctrl(ssl,SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB,(void (*)(void))cb)
 
 # define TLS1_FINISH_MAC_LENGTH          12
 
-# define TLS_MD_MAX_CONST_SIZE                   20
+# define TLS_MD_MAX_CONST_SIZE                   22
 # define TLS_MD_CLIENT_FINISH_CONST              "client finished"
 # define TLS_MD_CLIENT_FINISH_CONST_SIZE         15
 # define TLS_MD_SERVER_FINISH_CONST              "server finished"
@@ -797,6 +797,8 @@ SSL_CTX_callback_ctrl(ssl,SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB,(void (*)(void))cb)
 # define TLS_MD_IV_BLOCK_CONST_SIZE              8
 # define TLS_MD_MASTER_SECRET_CONST              "master secret"
 # define TLS_MD_MASTER_SECRET_CONST_SIZE         13
+# define TLS_MD_EXTENDED_MASTER_SECRET_CONST     "extended master secret"
+# define TLS_MD_EXTENDED_MASTER_SECRET_CONST_SIZE        22
 
 # ifdef CHARSET_EBCDIC
 #  undef TLS_MD_CLIENT_FINISH_CONST
@@ -846,6 +848,11 @@ SSL_CTX_callback_ctrl(ssl,SSL_CTRL_SET_TLSEXT_TICKET_KEY_CB,(void (*)(void))cb)
  * master secret
  */
 #  define TLS_MD_MASTER_SECRET_CONST    "\x6d\x61\x73\x74\x65\x72\x20\x73\x65\x63\x72\x65\x74"
+#  undef TLS_MD_EXTENDED_MASTER_SECRET_CONST
+/*
+ * extended master secret
+ */
+#  define TLS_MD_EXTENDED_MASTER_SECRET_CONST    "\x65\x78\x74\x65\x63\x64\x65\x64\x20\x6d\x61\x73\x74\x65\x72\x20\x73\x65\x63\x72\x65\x74"
 # endif
 
 /* TLS Session Ticket extension struct */